When transporting goods, for example, on cargo ships, trains and trucks, the goods are stored in containers for instance. The containers are often stacked on top of each other to allow a great cargo capacity to be transported simultaneously. Stacking of containers also occurs in storing of goods. Containers of this type, which are often referred to as ISO containers, allow the transported goods to be well protected during transport and also in loading and unloading.
Containers of the type described above are usually rectangular with floor, roof, two side walls and two end walls. At the corners of the containers, corner fittings are usually arranged, which are used to connect and lash containers. To connect and lash containers, lockable couplings are used as a rule, which can be inserted into and locked to a corner fitting of a container.
Lashing devices for lashing are frequently designed as stretching screws where the upper end of the stretching screw is fixed to a corner fitting of a container and the lower end of the stretching screw is fixed to the deck of the ship or a loading platform. It is also common for the upper end of the stretching screw to be fixed to a corner fitting of an upper container and the lower end of the stretching screw to be fixed to a corner fitting of a container which is positioned at one or more levels below the upper container.
In order to lash containers, the lashing system is tightened (stretched) by the stretching screw being tightened by rotation. After tightening of the lashing device, the stretching screw is usually locked by a check nut. It frequently happens that such check nuts can be released due to vibrations or the like during transport. If a check nut is released, there is a risk that the stretching screw is released, thus impairing the lashing or even making it cease. The operation of tightening a released check nut during transport may involve serious danger to an operator who is to perform this operation.
U.S. Pat. No. 6,666,634 discloses another lashing device where the stretching screw is secured after tightening by a locking seat with a non-cylindrical hole being moved into form-fit engagement with an end of the stretching screw. Locking of the described lashing device means that the end of the stretching screw is oriented in a certain position which conforms with the geometry of the seat to allow the two parts to be moved into engagement with one another.
Lashing often is a time-consuming operation which requires that the lashing device be simple and effective to handle. There is also a risk that the locking of the stretching screw is not ensured because this operation has not been correctly performed, which may cause serious consequences and involve great danger.